package demo;

import java.util.LinkedList;
import java.util.Queue;


//队列实现栈
public class MyStack {

    Queue<Integer> qu1;
    Queue<Integer> qu2;
    public int usedSize;

    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }

    public void push(int x) {
        if(!qu1.isEmpty()) {
            qu1.offer(x);
        }else if(!qu2.isEmpty()) {
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
    }

    public int pop() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int curSize = qu1.size();
            for (int i = 0; i < curSize; i++) {
                qu2.offer(qu1.poll());
            }
            usedSize--;
            return qu1.poll();
        }else {
            int curSize = qu2.size();
            for (int i = 0; i < curSize; i++) {
                qu1.offer(qu2.poll());
            }
            usedSize--;
            return qu2.poll();
        }

    }
    public int top() {
        if(empty()) {
            return -1;
        }
        if(!qu1.isEmpty()) {
            int curSize = qu1.size();
            int ret = -1;
            for (int i = 0; i < curSize; i++) {
                 ret = qu1.poll();
                 qu2.offer(ret);
            }
            return ret;
        }else {
            int curSize = qu2.size();
            int ret = -1;
            for (int i = 0; i < curSize; i++) {
                ret = qu2.poll();
                qu1.offer(ret);
            }
            return ret;
        }
    }




    public boolean empty() {
        return usedSize == 0;
    }

}
